Overrunning Alternator Decoupler Pulley with Bare Wire Spring and Grease Lubrication

ABSTRACT

A decoupler assembly is provided for a system that employs an endless power transmitting element. The decoupler includes a one-way clutch with a wrap spring and a torsion spring that are disposed between a pulley, which is engaged to the endless power transmitting element, and a hub. The one-way clutch permits overrunning of a driven or output one of the pulley and the hub, whereas the torsion spring stores and releases energy to attenuate the response of the one-way clutch in a manner that provides improved durability of an interface between the wrap spring and the pulley.

FIELD OF THE INVENTION

The invention relates to a belt drive assembly for driving belt drivenaccessories in an engine of an automotive vehicle, and moreparticularly, to a decoupling mechanism for allowing the belt drivenaccessories to operate temporarily at a speed other than the belt driveassembly.

DESCRIPTION OF THE PRIOR ART

It is widely known in an automotive vehicle engine to transfer a portionof the engine output to a plurality of belt driven accessories utilizingan endless serpentine belt. Typically, each component includes an inputdrive shaft and a pulley coupled to a distal end of the drive shaft fordriving engagement with the belt. An example of such a belt drivenaccessory is an alternator.

It is also known to provide a decoupler operatively coupled between thepulley and the alternator to allow the alternator drive shaft to“overrun” or rotate at a faster speed than the pulley and to allow thespeed of the pulley to oscillate with respect to the alternator driveshaft due to oscillations in the engine speed.

Examples of decouplers are disclosed in the U.S. Pat. No. 6,083,130,issued to Mevissen et al. on Jul. 4, 2000 and the U.S. Pat. No.5,139,463, issued to Bytzek et al. on Aug. 18, 1992.

It remains desirable to provide a decoupler that is easier tomanufacture and has better durability over conventional decouplerdesigns.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a decoupler assembly isprovided for transferring torque between a shaft and a drive belt. Thedecoupler assembly includes a hub configured to be fixedly secured tothe shaft. The hub includes a helical first slot formed therein. Acarrier is rotatably mounted on the hub. The carrier includes a helicalsecond slot formed therein. A torsion spring extends between a hub endand a carrier end for transferring torque between the hub and carrier,wherein the hub end is retained in the helical first slot to preventrelative movement between the hub end of the torsion spring and the huband the carrier end is retained in the helical second slot to preventrelative movement between the carrier end of the torsion spring and thecarrier. A pulley is rotatably coupled to the hub. The pulley includesan outer surface configured to frictionally engage with the drive belt.The pulley has an inner surface formed therein. A clutch spring isfixedly secured to the carrier and has a plurality of helical coilsfrictionally engaging with the inner surface of the pulley toselectively couple the hub and pulley. The torsion spring and the clutchspring are wound in opposite senses enabling the clutch spring to expandinto gripping engagement with the inner surface during acceleration ofthe pulley relative to the hub and to contract out of grippingengagement with the inner surface during deceleration of the pulleyrelative to the hub.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a front view of an engine of an automotive vehicleincorporating a decoupler assembly according to one aspect of theinvention;

FIG. 2 is an enlarged fragmentary sectional view of the decouplerassembly;

FIG. 3 is a perspective view of a clutch spring in the decouplerassembly;

FIG. 4 is a perspective view of a carrier for carrying one end of theclutch spring in the decoupler assembly;

FIG. 5 is a perspective view of the clutch spring assembled to thecarrier;

FIG. 6 is an exploded perspective view of the decoupler assemblyaccording to a second embodiment of the invention;

FIG. 7 is a cross sectional view of the decoupler assembly according tothe second embodiment of the invention; and

FIG. 8 is a cross sectional view of the decoupler assembly according toa third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures, an engine for an automotive vehicle isgenerally indicated at 10 in FIG. 1. The engine 10 includes a crankshaft12 driving an endless serpentine belt 14, as commonly known by thosehaving ordinary skill in the art. The engine 10 also includes a beltdriven accessory 16 driven by the belt 14. Described in greater detailbelow, a decoupler assembly 20 is operatively assembled between the belt14 and the belt driven accessory 16 for automatically decoupling thebelt driven accessory 16 from the belt 14 when the belt 14 deceleratesrelative to the belt driven accessory 16 and allowing the speed of thebelt 14 to oscillate relative to the belt driven accessory 16.Additionally, a detailed description of the structure and function of adecoupler assembly can be found in applicant's U.S. Pat. No. 6,083,130,which issued on Jul. 4, 2000 and is incorporated herein by reference inits entirety.

Referring to FIG. 2, the decoupler assembly 20 includes a hub 22 havingopposite first 24 and second 26 ends and a generally cylindrical body 28extending axially therebetween. The body 28 includes opposite inner 30and outer 32 surfaces extending between the first 24 and second 26 endsof the hub 22. The inner surface 30 includes a plurality of innerthreads 33 adjacent the first end 24 for fixedly securing the hub 22 toa drive shaft 15 from the belt driven accessory 16. A reduced diameterportion 34 is formed in the first end 24. The reduced diameter portion34 includes an outer mounting surface 36 having a smaller outer diameterthan the body 28. An abutment surface 38 opposite the second end 26extends generally radially between the outer mounting surface 36 and thebody 28. An annular thrust washer 39 is seated on the outer mountingsurface 36 adjacent the abutment surface 38.

A socket 40 is formed in the second end 26 for receiving a suitable tooltherein for rotatably threading the hub 22 onto the drive shaft 15. Anannular first flange 41 extends radially outwardly from the body 28adjacent the second end 26. The first flange 41 includes an outer flangesurface 42 having a larger outer diameter than the body 28. An annularsurface 44 extends generally radially between the body 28 and the outerflange surface 42 opposite the second end 26. A generally helical firstslot 46 is formed in the annular surface 44 defining a first locatingsurface 48 therein.

A generally cylindrical pulley 50 is rotatably journaled to the hub 22.More specifically, the pulley 50 extends between opposite first 52 andsecond 54 ends. The pulley 50 includes an inner surface 56 extendingbetween the first 52 and second 54 ends. A ball bearing member 57 iscoupled between the pulley 50 and the hub 22. The bearing member 57includes an inner race 58 fixedly secured to a portion of the outermounting surface 36 and an outer race 59 fixedly secured to a portion ofthe inner surface 56 adjacent the first end 52 of the pulley 50. Aplurality of ball bearings 55 is rollingly engaged between the inner 58and outer 59 races of the bearing member 57. A cylindrical bushing 60 isjournal mounted between the pulley 50 and the first flange 41. Thebushing 60 includes a sleeve wall 62 extending between a portion of theinner surface 56 adjacent the second end 54 and the outer flange surface42 of the first flange 41. A bushing bushing flange 64 extends radiallyinwardly from the sleeve wall 62 and abuts the annular surface 44 in thefirst flange 41.

The pulley 50 includes an outer periphery 66 with a plurality ofV-shaped grooves 68 formed therein for rollingly engaging and guidingthe belt 14.

Referring to FIGS. 2-5, a one-way clutch assembly 70 is operativelycoupled between the hub 22 and the pulley 50. The clutch assembly 70includes a clutch spring 71 and a carrier 75. The clutch spring 71includes a plurality of helical coils 72 extending between a bent orhooked proximal end 73 and an opposite distal end 74. Preferably, theclutch spring 71 is formed from an uncoated, spring steel material andhas a non-circular cross-section to improve frictional contact. Mostpreferably, the cross-section of clutch spring 71 is rectangular orsquare. The clutch spring 71 is press fitted into frictional engagementwith the inner surface 56 of the pulley 50. Preferably, a lubricantsimilar or compatible with grease used in the ball bearing member 57 isapplied to minimize wear between the clutch spring 71 and the innersurface 56 of the pulley 50.

The carrier 75 is rotatably mounted on the hub 22. The carrier 75 isgenerally ring shaped and extends axially between opposite first andsecond sides 76, 78. A hooked slot 84 is formed in the second side 78 ofthe carrier 75 and is configured to retain the hooked proximal end 73 ofthe clutch spring 71. A generally helical second slot 86 is formed inthe second side 78 of the carrier 75 defining a second locating surface88 generally opposing the first locating surface 48 formed in theannular surface 44.

Referring to FIG. 2, a helical torsion spring 90 extends between hub 92and carrier 94 ends. The torsion spring 90 is axially compressed betweenthe first 48 and second 88 locating surfaces for transferring torquebetween the hub 22 and the carrier 75. More specifically, the hub end 92of the torsion spring 90 is retained in the first slot 46 of the hub 22.Similarly, the carrier end 94 of the torsion spring 90 is retained inthe second slot 86 in the second side 78 of the carrier 75. Axial forcesdue to the compression of the torsion spring 90 retains the first side76 of the carrier 75 in abutting engagement with the thrust washer 39.The torsion spring 90 also allows relative movement between the carrier75 and the hub 22 to accommodate changes in the speed of the pulley 50due to generally oscillating changes in the operating speed of theengine. The torsion spring 90 and the clutch spring 71 are coiled inopposite directions.

A cap 100 is fixedly assembled to a flange 102 formed in the pulley 50for preventing contaminants from entering the decoupler assembly 20 andfor retaining the lubricant within the decoupler assembly 20.

In operation, the engine 10 is started and the pulley 50 is acceleratedand rotated in a driven direction by the belt 14 driven by the engine10. Acceleration and rotation of the pulley 50 in the driven directionrelative to the hub 22 creates friction between the inner surface 56 ofthe pulley 50 and preferably all of the coils 72 of the clutch spring71. It should be appreciated that the clutch spring 71 will functioneven where at the onset at least one of the coils 72 of the clutchspring 71 is frictionally engaged with the inner surface 56 of thepulley 50. The clutch spring 71 is helically coiled such that thefriction between the inner surface 56 of the pulley 50 and at least oneof the coils 72 would cause the clutch spring 71 to expand radiallyoutwardly toward and grip the inner surface 56 of the pulley 50.Continued rotation of the pulley 50 in the driven direction relative tothe hub 22 would cause a generally exponential increase in the outwardlyradial force applied by the coils 72 against the inner surface 56 untilall of the coils 72 of the clutch spring 71 become fully brakinglyengaged with the pulley 50. When the clutch spring 71 is fully engagedwith the inner surface 56, the rotation of the pulley 50 is fullydirected toward rotation of the drive shaft 15 of the belt drivenaccessory 16. Additionally, centrifugal forces help to retain the clutchspring 71 in braking engagement with the inner surface 56 of the pulley50.

The rotational movement of the carrier 75 in the driven direction istransferred to the hub 22 by the torsional spring 90 such that generallythe carrier 75, thrust washer 39, hub 22, and the drive shaft 15 fromthe belt driven accessory 16 rotate together with the pulley 50.Additionally, the torsional spring 90 resiliently allows relativemovement between the carrier 75 and the hub 22 to accommodateoscillations in the speed of the pulley 50 due to correspondingoscillations in the operating speed of the engine 10.

When the pulley 50 decelerates, the hub 22 driven by the inertiaassociated with the rotating drive shaft 15 and the rotating mass withinthe belt driven accessory 16 will initially “overrun” or continue torotate in the driven direction at a higher speed than the pulley 50.More specifically, the higher rotational speed of the hub 22 relative tothe pulley 50 causes the clutch spring 71 to contract radially relativeto the inner surface 56 of the pulley 50. The braking engagement betweenthe clutch spring 71 and the pulley 50 is relieved, thereby allowingoverrunning of the hub 22 and drive shaft 15 from the belt drivenaccessory 16 relative to the pulley 50. The coils 72 may remainfrictionally engaged with the inner surface 56 while the pulley 50decelerates relative to the clutch assembly 70 and the hub 22. The coils72 of the clutch spring 71 begin to brakingly reengage the inner surface56 as the pulley 50 accelerates beyond the speed of the hub 22.

Referring to FIGS. 6 and 7, a second embodiment of the decouplerassembly 20′ is shown, wherein elements of the alternative embodimentsimilar to those in the first embodiment are indicated by primedreference characters. The decoupler assembly 20′ is assembled between anoutput or crankshaft 106 of an engine and the belt 14′ to allow the belt14′ to overrun the crankshaft 106. The decoupler assembly 20′ includes agenerally ring-shaped spring support 110. The slot 46′ of the hub 22′has a generally U-shaped cross section for retaining the spring support110 therein.

A first tab 112 extends outwardly from the spring support 110. A firstnotch 114 is formed in the hub end 92′ of the torsion spring 90′ foraxially receiving the first tab 112 therein. Engagement between thefirst tab 112 and the first notch 114 prevents relative rotationalmovement of the hub end 92′ of the torsion spring 90′ relative to thespring support 110 and hub 22′. Similarly, a second tab 116 extendsoutwardly from the second locating surface 88′ of the carrier 75′. Asecond notch 118 is formed in the carrier end 94′ of the torsion spring90′ for axially receiving the second tab 116 therein. Engagement betweenthe second tab 116 and the second notch 118 prevents relative rotationalmovement of the carrier end 94′ of the torsion spring 90′ relative tothe carrier 75′.

The pulley 50′ includes an outer periphery 120 for seating the belt 14′therein and an inner flange portion 122. The inner flange portion 122has a generally U-shaped cross section defined by outer 124 and inner126 pulley walls and a first connecting wall 128 extending radiallytherebetween. The carrier 75′ is retained between the outer 124 andinner 126 pulley walls and the first connecting wall 128 of the innerflange portion 122, such that the carrier 75′ rotates with the pulley50′. A second connecting wall 130 extends radially between the outerpulley wall 124 and the outer periphery 120.

The carrier 75′ includes a slot or split 132, which helps the carrier75′ to flex and accommodate loads associated with the rotation of thedecoupler assembly 22′.

Referring to FIG. 8, a third embodiment of the decoupler assembly 20″ isshown, wherein the body 28″ and first flange 41″ of the hub 22″ areformed separately and fixedly connected in a subsequent assemblyoperation. The body 28″ of the hub 22″ is generally cylindrical andextends between the first 24″ and second 26″ ends. The first flange 41″includes a mounting portion 140, which has a center bore 142 forreceiving the outer flange surface 36″ of the hub 22″ therethrough. Thefirst flange 41″ includes a generally U-shaped cross section defined byan end wall 134 extending radially between generally parallel inner 136and outer 138 flange walls. The spring support 110″ is retained betweenthe inner 136 and outer 138 flange walls and the end wall 134, such thatthe spring support 110″ rotates with the first flange 41″.

The outer periphery 120″ and the inner flange portion 122″ of the pulley50″ are formed separately and fixedly connected in a subsequent assemblyoperation using any suitable method, such as welding. The generallyU-shaped cross section of the inner flange portion 122″ opens toward thefirst flange 41″. The carrier 75″ is retained between the outer 124″ andinner 126″ pulley walls and the first connecting wall 128″, such thatthe carrier 75″ rotates with the pulley 50″.

A ring plate 143 is mounted concentrically onto the outer mountingsurface 36″ adjacent the abutment surface 38″. A thrust washer 144 isdisposed between the first flange 41″ and the ring plate 143. The thrustwasher 144 is axially spaced apart from the end wall 134 of the flange41″ for receiving the inner flange portion 122″ of the pulley 50″therebetween.

A torsional vibration damper 146, as known by those skilled in the art,is fixedly secured to the outer flange wall 138 of the first flange 41″for dampening vibrations experienced at the crankshaft 106 associatedwith the operations of the engine.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology, which has been used, is intended tobe in the nature of words of description rather than of limitation. Manymodification and variations of the present invention are possible inlight of the above teachings. It is, therefore, to be understood thatwithin the scope of the appended claims, the invention may be practicedother than as specifically described.

1-29. (canceled)
 30. A decoupler assembly comprising: a hub that isadapted to be coupled to a shaft such that the shaft co-rotates with thehub; a carrier that is rotatable relative to the hub; at least onetorsion spring between the hub and the carrier; a pulley having an outerperiphery, which is adapted to engage an endless power transmittingelement, and an inner surface; and a clutch spring formed only of wire,the clutch spring having a first end that is received in a groove formedin the carrier, a second end opposite the first end and a plurality ofcoils between the first and second ends, the clutch spring exiting thecarrier and extending toward the inner surface of the pulley such thatat least one of the plurality of coils is engaged against the innersurface of the pulley when rotary power is transmitted between thepulley and the hub, the plurality of coils contracting to reducegripping engagement with the inner surface of the pulley in response todeceleration of the pulley relative to the carrier beyond apredetermined extent.
 31. The decoupler assembly of claim 30, whereinthe clutch spring exits the carrier in a radially outward direction. 32.The decoupler assembly of claim 30, wherein the at least one torsionspring and the clutch spring are coiled in opposite directions.
 33. Thedecoupler assembly of claim 30, wherein the at least one torsion springuncoils as a magnitude of the rotary power transmitted between thecarrier and the hub increases.
 34. The decoupler assembly of claim 33,wherein at least one of the carrier and the hub includes a tapered rampand an abutting wall that is perpendicular to the tapered ramp andwherein the at least one torsion spring abuts each of the abuttingwalls.
 35. The decoupler assembly of claim 30, wherein the carrier ismounted on the hub.
 36. The decoupler assembly of claim 30, wherein thewire has a cross-sectional shape with an outer side that abuts the innersurface of the pulley, the outer side having a contour that isconfigured to distribute load transmitted from the clutch spring to thepulley over multiple points of contact spaced along the outer side. 37.The decoupler assembly of claim 36, wherein the outer side has a flatcontour.
 38. The decoupler assembly of claim 37, wherein the wire has asquare cross-sectional shape or a rectangular cross-sectional shape. 39.The decoupler assembly of claim 30, wherein the wire has across-sectional shape with an outer side, which abuts the inner surfaceof the pulley, and lateral sides that are coupled to the oppositelateral sides of the outer side, the lateral sides having a flatcontour.
 40. The decoupler assembly of claim 39, wherein the wire has asquare cross-sectional shape or a rectangular cross-sectional shape. 41.The decoupler assembly of claim 30, wherein the at least one torsionspring is axially compressed between the carrier and the hub.
 42. Thedecoupler assembly of claim 30, further comprising a bearing disposedbetween the hub and the pulley.
 43. The decoupler assembly of claim 30,wherein the plurality of coils are abutted against one another.
 44. Thedecoupler assembly of claim 30, further comprising a torsional vibrationdamper fixed for rotation with the hub.
 45. The decoupler assembly ofclaim 30, wherein the groove is formed on an axial end face of thecarrier.
 46. The decoupler assembly of claim 30, further comprising alubricant disposed on coils of the clutch spring.
 47. The decouplerassembly of claim 46, wherein the lubricant is a grease.
 48. Thedecoupler assembly of claim 46, wherein the clutch spring exits thecarrier in a radially outward direction.
 49. The decoupler assembly ofclaim 46, wherein the at least one torsion spring and the clutch springare coiled in opposite directions.
 50. The decoupler assembly of claim46, wherein the at least one torsion spring uncoils as a magnitude ofthe rotary power transmitted between the carrier and the hub increases.51. The decoupler assembly of claim 50, wherein at least one of thecarrier and the hub includes a tapered ramp and an abutting wall that isperpendicular to the tapered ramp and wherein the at least one torsionspring abuts each of the abutting walls.
 52. The decoupler assembly ofclaim 46, wherein the carrier is mounted on the hub.
 53. The decouplerassembly of claim 46, wherein the wire has a cross-sectional shape withan outer side that abuts the inner surface of the pulley, the outer sidehaving a contour that is configured to distribute load transmitted fromthe clutch spring to the pulley over multiple points of contact spacedalong the outer side.
 54. The decoupler assembly of claim 53, whereinthe outer side has a flat contour.
 55. The decoupler assembly of claim54, wherein the wire has a square cross-sectional shape or a rectangularcross-sectional shape.
 56. The decoupler assembly of claim 46, whereinthe wire has a cross-sectional shape with an outer side, which abuts theinner surface of the pulley, and lateral sides that are coupled to theopposite lateral sides of the outer side, the lateral sides having aflat contour.
 57. The decoupler assembly of claim 56, wherein the wirehas a square cross-sectional shape or a rectangular cross-sectionalshape.
 58. The decoupler assembly of claim 46, wherein the at least onetorsion spring is axially compressed between the carrier and the hub.59. The decoupler assembly of claim 46, further comprising a bearingdisposed between the hub and the pulley.
 60. The decoupler assembly ofclaim 46, wherein the plurality of coils are abutted against oneanother.
 61. The decoupler assembly of claim 46, further comprising atorsional vibration damper fixed for rotation with the hub.
 62. Thedecoupler assembly of claim 46, wherein the groove is formed on an axialend face of the carrier.
 63. A decoupler assembly comprising: a hub thatis adapted to be coupled to a shaft such that the shaft co-rotates withthe hub; a carrier that is rotatably mounted on the hub; at least onetorsion spring between the carrier and the hub; a pulley having an outerperiphery, which is adapted to engage an endless power transmittingelement, and an inner surface; and a clutch spring formed only of wire,the clutch spring having a plurality of coils, wherein less than onecomplete coil is engaged to the carrier, wherein at least one of theplurality of coils is engaged against the inner surface of the pulleywhen rotary power is transmitted between the pulley and the hub, atleast a portion of the plurality of coils contracting to reduce grippingengagement with the inner surface of the pulley in response todeceleration of the pulley relative to the carrier beyond apredetermined extent.
 64. The decoupler assembly of claim 63, furthercomprising a lubricant disposed on coils of the clutch spring.
 65. Thedecoupler assembly of claim 64, wherein the lubricant is a grease.